Crate resext 

resext provides simple, lightweight, low-cost error-handling methods in Rust without losing ergonomics.

The main points of this crate are:

1. ResExt: Error-handling trait

A trait that provides methods for error-handling which is implemented for Result<T, E>, so you can just import it in your project like this:

use resext::ResExt;

• and use all the methods it provides for Result<T, E>!

2. ErrCtx<E>: Custom error struct

This is the main struct ResExt uses to add context to errors.

It stores two fields:

1. msg: Vec<u8> which is the field that stores all context messages in the chain in raw bytes for more optimized memory usage than storing actual string messages.
2. source: E where E: std::error::Error which stores the source that the context originated from (e.g. std::io::Error::other("")).

Example

use resext::*;
use std::io::{Error, ErrorKind::InvalidInput};
use serde_json::Value;

fn process_logs() -> CtxResult<Value, Error> {
    let path: &str = "log.json";

    let content = std::fs::read_to_string(path)
        .context("Failed to process logs.")
        .with_context(|| format!("Failed to read logs file: {}.", path))?;

    let logs: Value = serde_json::from_str::<Value>(&content)
        .map_err(|_| Error::new(InvalidInput, "Invalid JSON input in file."))
        .context("Failed to parse logs for processing.")
        .with_context(|| format!("Invalid JSON in logs file: {}.", path))?;

    logs
}

• Output for first Result on error:

Failed to process logs.
- Failed to read logs file: log.json.
Caused by: NotFound

• Output for second Result on error:

Failed to parse logs for processing.
- Invalid JSON in logs file: log.json.
Caused by: InvalidInput

You can chain more context of course, this is just an example.

---

This crate is licensed under the MIT license.

Macros

throw_err_if

Throw an error if condition is true.

Structs

ErrCtx

Custom error struct ErrCtx.

Traits

ResExt

Type Aliases

CtxResult

Type alias for Result<T, ErrCtx<E>>.